This invention is directed to a timed switch for AC loads and in particular to a switching apparatus for disconnecting a load from a source at a preselected time after the load has been energized.
Over the years, an ever increasing need has been felt for a form of wall switch which will automatically turn off the lights in an area which is not occupied. Many timing devices have been developed but are normally found to be complex to install since they require a separate supply of power. A device that does not need a separate supply is described in U.S. Pat. No. 3,940,660 which issued to F. H. Edwards on Feb. 24, 1976. This device is powered from across the triac switch which itself is in series with the load. However, this switch requires a substantial amount of supply power which is absorbed either during a substantial portion of the beginning of each AC cycle or during 1 out of N cycles when the load is not connected to the source. Flickering is apparent in incandescent lamp loads and particularly in fluorescent lamp loads.